The present invention relates to new and useful improvements in semi-permeable membrane separation equipment and in particular to means for housing and mounting membrane separation units in operative relationship within a casing.
In general use semi-permeable membrane separation units or cartridges are arranged within a casing or module assembly and function to separate a selected product or products from a carrier liquid fed to the separation unit. In one mode of use a pressure differential is maintained across the membrane surface as the product carrying liquid is fed under pressure across one side of the membrane surface. Liquid and selected dissolved solids are passed through pores in the membrane surface as a permeate product to a discharge outlet in the casing. The carrier liquid that is not passed through the membrane becomes concentrated with solids and which solids in certain processes is the product until a selected concentration level of solids is reached. The concentrated liquid is then drawn out of the casing and transmitted either to waste or returned to the process in accordance with the predetermined objectives of the particular separation process. Alternatively the permeate may be wasted, returned to process or otherwise utilized.
Membrane separation equipment of the general type mentioned is used in a wide variety of reverse osmosis and ultrafiltration processes. Among other presently well known uses of this equipment, but not limited thereto, are the processing of paint in electro-deposition processes; treatment of waste water; desalination processes; and in food processing such as the treatment of cheese whey.
In this equipment a variety of structures or cartridge assemblies have been used for supporting the membranes. In one type the membranes are formed on porous surfaces and wound into a spiral tube through which the carrier liquid is transmitted. In other units the membrane separation units are tubular in shape. Still another type cartridge unit is disclosed in U.S. Pat. No. 3,494,465 and includes porous sheets mounted on a supporting plate with the membranes formed on both sides of the porous sheets. The permeate passes through the membrane to the porous sheet and is then fed to the supporting plate. Specially designed casing structure is provided for housing these cartridges and which structure is complementary with the supporting plate for receiving the permeate. The casings are also provided with suitable outlets for the permeate output flow and the concentrated carrier liquid output.
In these known units the surface area available for membrane filtration is limited by the specially formed casing construction and cartridge structure. As a result the capability of external pump capacity for circulating the carrier liquid through the casing is also limited. In addition to the reduced separation capacity as the membrane surface area is reduced, there is a corresponding decrease in the volume of carrier liquid that can be processed through the unit. In known casings difficulties are also present in providing ready access to the cartridges for inspection and replacement. The latter problems are further complicated by the relatively complex casing structure and specially configurated wall portions for mounting the cartridges and providing suitable permeate outlets and the like.
It is an object of the present invention to provide a novel canister casing for housing semi-permeable membrane cartridges.
Another object is to provide a novel canister for supporting therein a plurality of membrane separation cartridges in parallel-series relationship.
A further object is to provide a canister wherein novel means are provided for circulating carrier liquid through the housing and wherein the overall surface area available for separation is increased while the overall size of the canister housing is reduced.
A still further object is to provide a novel canister wherein means are provided for permitting ready access to the separation cartridges and further include means for allowing ready removal and replacement thereof from the canister housing.